1. Field of the Invention
The present invention relates in general to a hybrid transmission for wheeled motor vehicles, and more particularly to a two-rotor type motor/generator unit that constitutes an essential part of the hybrid transmission. More specifically, the present invention is concerned with a supporting structure for rotatably supporting an outer rotor or outer rotor assembly of the motor/generator unit relative to a housing.
2. Description of the Related Art
In order to clarify the task of the present invention, a hybrid transmission and a two-rotor type motor/generator unit of the hybrid transmission to which the present invention is practically applied will be briefly described in the following.
The hybrid transmission generally comprises a housing, a differential speed change unit installed in the housing and a two-rotor type motor/generator unit installed in the housing in a manner to be coaxial with the speed change unit. Upon mounting on a motor vehicle, the hybrid transmission is positioned beside an engine (viz., internal combustion engine) in such an arrangement that speed change unit is placed between the motor/generator unit and the engine.
The two-rotor type motor/generator unit generally comprises inner and outer rotors that rotate about a common axis in and around a fixed annular stator respectively. Inner and outer rotor shafts are concentrically arranged about the common axis and extend from the inner and outer rotors to the speed change unit to be operatively connected to the same. The inner rotor shaft is a hollow member and the outer rotor shaft is rotatably received in the inner rotor shaft. The inner rotor shaft has an axially outside end portion tightly engaged with an inner cylindrical wall of the inner rotor, so that the inner rotor shaft and the inner rotor rotate like a single unit.
The outer rotor shaft received in the hollow inner rotor shaft has an axially outside end that is connected to an outside end of the outer rotor through a circular drive plate, so that the outer rotor shaft, the drive plate and the outer rotor rotate like a single unit. More particularly, the circular drive plate is positioned at an axially outside end of the motor/generator unit that is opposite to an axially inside end of the same that faces the speed change unit. That is, the outer rotor is connected to the speed change unit through a so-called “turn-around power transmission structure”.